London’s tornado

On the evening of Saturday 25 June 2021, the East London suburb of #Barking was struck by something rather unexpected: a #tornado. The #twister brought down some brick walls and sent domestic bins flying but fortunately, there were no reports of casualties. Whilst this event was nothing like the scale of those we see in #TornadoAlley in America’s mid-west (where whole towns can be flattened), it would nonetheless have been terrifying for residents of this unassuming town on the Thames.

Tornado-attributable damage in Barking (source).

In truth, what happened late last week in Barking is not really that rare or unusual. According to the Met Office, the UK experiences around 30 tornadoes per year but fortunately, most of these are small and/or occur in relatively rural locations and thus go unnoticed. This isn’t always the case however. In 2005, a tornado struck Birmingham (UK), cutting through the city’s suburbs and leaving a trail of destruction 7 km long (see below).

The track of Birmingham’s 2005 tornado (north is towards the right of this image).

Another British event that is noteworthy occurred in November 1981. Over a period of 6 hours, the UK was struck by a swarm of 104 tornadoes, making it Europe’s largest ever tornado swarm. Damage was inflicted nationwide, from Birmingham, through to Manchester and across to Anglesey. This swarm event actually ranks as one of the biggest ever recoded worldwide. In the main however, European tornadoes are usually orders of magnitude smaller than those witnesses in the USA.

The damage associated with the 63 km track of a tornado that struck Massachusetts in 2011 (source).

Tornadoes occur when there is a strong vertical wind shear i.e. when the speed and direction of winds varies significantly with altitude (see below). This is commonly experienced when different air masses of different temperature and water content meet - something that is common both in Northern Europe (Mediterranean vs Arctic) and the US Mid-West (Canadian vs. Caribbean). If intense enough, the resulting storms become #supercell storms and it is these that generally generate tornadoes. The event in London a few days ago was associated with a slow-moving thunderstorm.

Visualising wind shear: it’s effect on landing aircraft.

Now we can’t talk about weather phenomena such as tornadoes without touching on the ever present issue of #climatechange and global warming. Most climate models used to predict future changes will not have a spatial resolution capable of envisioning tornadoes (which are usually measured on the scale of metres) but they are capable of modelling changes in atmospheric temperature and water content, and in air masses and other conditions that generate severe storms. Evidence points to the fact that #globalwarming will probably lead to more powerful storms but this doesn’t necessarily mean more tornadoes (indred, not all powerful storms generate them). Evidence does in fact show an increase in tornadoes over recent decades, but this is largely due to improved monitoring and recording as opposed to more actual events (previously, many went unnoticed). In summary, the jury of out as to the effect of climate change on future tornado frequency.

Our warming planet (source).

Most Brits will be aware that our home country is relatively safe when it comes to natural #hazard events but this tornado should perhaps open our eyes to the fact that we’re not completely immune to the ravages of nature. Most things this side of the Atlantic pond are smaller than those stateside and in this case, I’m very much content with that!